Habitat characteristics for different freshwater snail species as determined biologically through macroin- vertebrate information

Macro-invertebrates including freshwater snails collected from 643 sites over 8 successive seasons among the River Nile, branches, main canals and certain drains in eight Egyptian Governorates. Thirteen snail species and one bivalve species were identified. The most distributed were Lanistus carinatus and Physa acuta while the most abundant were Cleopatra bulimoides and Physa acuta during the whole study. The sites that harbored each snail species in all the examined watercourses were grouped seasonally and their biological assessment was determined by their minimum and maximum total point similarity percentage to that of the corresponded reference site and mean of the total points. Habitats for most snail species attained minimum total point's similarity percentage less than 21% [very poor habitat] during autumn and winter then spring while during summer very poor habitat was harbored by only few snail species. P. acuta was the only survived snails in habitat which attained 0 as a minimum total point's similarity percentage during two seasons and L. carinatus and Succinea cleopatra during one season. With respect to medically important snails very poor sites constituted 23% of Biomphalaria alexandrina sites, 14% of Lymnaea natalensis and 9.4% of Bulinus truncatus sites. The studied macroinvertebrate matrices, total number of organisms, taxa richness, the Ephemeroptera, Plecoptera, and Trichoptera [EPT] index, ratio of EPT index to chironomidae, ratio of scraper to filtering collector, contribution of dominant macroinvertebrate major group, comparison revealed descending tolerances from B. alexanrina followed by L. natalensis then B. truncates, but Hilsenhoff Biotic Index [HBI] showed the same tolerance to organic pollution

Chemical and biological assessment for Egyptian surface freshwater environment with reference to human activities

The Egyptian freshwater was assessed in the River Nile, branches, main canals and certain drainages in eight Governorates, over eight successive seasons starting from spring 2008. Chemical assessment was made through ten parameters and the biological one was made through macro-invertebrates information. Results showed that means of Cd, Pb, Cu, Hg, Mn, Fe, Ni, Na, K and Ca varied in watercourses seasonally within somewhat narrow ranges, which may exceed the level of concern but with some elevations in branches, Rayahs and canals during certain seasons. Sites showed chemical levels over the permissible one or those gain total points

Determination of allozyme, protein and schistosome susceptibility in biomphalaria alexandrina progenies produced by self and cross fertilization

The mating system of B. alexandrina was studied under laboratory condition by allozyme analysis and SDS-PAGE protein analysis for parent snails and their progenies of two successive generations produced by self and cross fertilization. Allozyme analysis detected 11 genetic loci in 3 enzymes; ACP [3 loci], LDH [2 loci] and EST [6 loci]. The mean number of Allele [A], average heterozygosity over loci [H] and dendrogram from cluster analysis based on genetic distances between snail groups showed a genetic heterogeneity in parents and 1[st] generation higher than that in the 2[nd] generation. Cross-fertilization and genetic heterogeneity among snails decreased through generations. Snails practiced self-fertilization showed genetic alterations and genetic heterogeneity was either decreased or increased. SDS-PAGE profile of tissue protein revealed that the mating system in B. alexandrina showed specific bands, 204 and 214 KDa, in snails bred by self-fertilization. D value based on shared protein bands number and estimated similarity between parents and progenies showed that parents were approximately similar with self and cross progenies in 1[st] generation and only with cross progenies in 2[nd] generation as self progenies showed increase or decrease in similarity. B. alexandrina susceptibility to S. mansoni was not affected when snails were bred by cross or self fertilization

Correlation between ovicidal effectiveness and egg-membrane penetration determined by chromatography in two modes of biomphalaria Alexandrina eggs exposure to certain plant and chemical molluscicides

The weak ovicidal effect of the plants having molluscicidal activity is a criterion against their field application in controlling the medically important snails. Chemical molluscicides are potent against snails and their eggs. This work is a trail to use bayluscide and CuSO4 [chemical molluscicides] in sub lethal concentrations to improve the ovicidal effect of Anagallis arvensis and Calendula micrantha plants against the eggs of Biomphalaria alexandrina snails through two modes of eggs exposure. The first was the pre-exposure of snail's eggs to sub lethal concentrations of chemical molluscicides followed by plant exposure and this improve the effect of plants against the snail's eggs with a synergistic ratio ranged from 1.5 to 4.49. While the second mode of exposure is to evaluate the toxicity of mixtures of chemical molluscicides and plants against snail's eggs. It was noticed that this moda resulted in 100% mortality when eggs exposed to mixture of LC15 of C. micrantha or LC25 of A. arvensis with sublethal concentrations of the molluscicides bayluscide or copper sulphate. TLC reveals that the number of the penetrated plant compounds increased in all copper sulphate treatments and in pre-exposure of C. micrantha by bayluscide while the same number of plant compounds were penetrated in the rest of bayluscide treatments as in the cese of the plant alone. So, the increase in plant potency was through chemicals that affect the eggs' membrane to be permeable for more active ingredients [more in number or concentration or both of them] of the tested plants to become in contact with the target embryos

Electrophoretic analysis of acid phosphatase in Biomphalaria alexandrina and its relation to susceptibility to Schistosoma mansoni infection

Enzyme electrophoresis of extracts prepared from snails collected from five different localities in Egypt and their progenies through the successive generations, were stained for acid phosphatase [ACP], exhibited mainly three electrophoresis patterns. The first which presented with three bands [R[f] 33+/1, 27 +/- and 23+/1], the second with two bands [R[f]33+/1 and 23+/1] and the third with one band [R[f] 23+/1]. In order to examine the relation of ACP henotypes with susceptibility or refractory characters to Schistosoma mansoni infection in B. alexandrina, the percentage of these phenotypes were calculated and compared among susceptible and non-susceptible snails. There was no correlation between ACP henotypes and the susceptibility of snails from different populations, and the percentage of the pattern two of ACP [exapressign resistance to schistosome infection] was approximately the same in susceptible and non-susceptible snails. Polymorphism of ACP patterns observed in the field snails and their first generation began to decrease through generations in both susceptible and non-susceptible snails and the one-banded pattern became predominant

Semifield trials to control biomphalaria Alexandrina by different modes of exposure to certain plant and chemical molluscicides

Semi-field trials were carried out in Snail Research Station under simulated natural conditions to evaluate different modes of exposure to Anagallis arvensis and Calendula micrantha as plant molluscicides and bayluscide and copper sulphate as chemical molluscicides. Firstly, B. alexandrina were exposed to the tested molluscicides alone and in addition to two densities of aquatic plants. No apparent effect of aquatic plants on the activity of both plant and chemical molluscicides, this may be due that the two densities of the aquatic plants used were insufficient to interfere with the molluscicides action. Secondly, snails were pre-exposed to three sub-lethal concentrations of the plant molluscicides for 24h then to three concentrations of the chemical molluscicides and vice versa. The results indicate that the pre-exposure increases the snail mortality significantly in all treatments of bayluscide and A. arvensis [except in the highest concentration when the snails firstly exposed to bayluscide then to A. arvensis, where the two compared treatment showed 100%] and in all treatments of bayluscide and C. micrantha. Also, in one treatment of copper sulphate and A. arvensis [in the highest concentration when the snails firstly exposed to A. arvensis then to copper sulphate] and in three treatments of copper sulphate and C. micrantha, [in least and moderate concentrations when snails firstly exposed to C. micrantha then to copper sulphate and in the highest concentration when snails firstly exposed to copper sulphate then to C. micrantha]. Thirdly, snails were exposed to mixtures of six different ratios of hayluscide and each of A. arvensiS and C. micrantha. The results indicated that the snail mortality increased significantly only in the first treatient of bayluscide and A. arvensis mixtures and in treatment number 6 of bayluscide and C. micrantha